Then pour a capful of this into the bucket and mix.

杰：将一瓶盖倒入桶并混合。

After she puts this capful of liquid into the bucket, Helen is supposed to mix it.

在她将这一瓶液体放入桶，海伦应该将其混合。

A " capful" would be the amount of liquid that would fit into the cap of the bottle.

“capful”将是适合瓶盖的液体量。

Notice there's just one " l" in " capful" even though the word " full" normally has two " l" s.

请注意，“capful”有一个“l”，尽管“full”一词通常有两个“l”。

So Jerry tells Helen " to pour" (pour) the liquid into the cap until she has a " capful." " Pour" means to move liquid from one container to another.

于是杰告诉海伦把液体“倒”（pour）到瓶盖里，直到她有一个“满满的”。“倒”的意思是把液体从一个容器移到另一个容器。